The use of magnetic products in such applications as automobiles, aircraft, reprographics equipment, telecommunications, computer and peripherals, and electronic security systems has long been recognized and new applications are being realized everyday. These products often call for magnets having various characteristics such as high magnetic field strength, magnetic field uniformity, flexibility, durability, and low cost.
One such product, used in the reprographics industry, is a magnetic roll, or magnetic development roll. In reprographic recording, a magnetic roll is concentrically surrounded by a toner tube. In operation, the toner tube is rotated relative to the magnetic roll about a common axis. The magnetic roll in combination with the toner tube is effective for conveying ferromagnetic toner powder from a powder material container onto a photoreceptor thus effecting an electrostatic image. The resultant toner image formed is then transferred to paper and fixed thereto by heating and/or pressing.
Recent demand for high image quality has called for the use of finer magnetic particles as toner materials. As a result, magnetic rolls require higher magnetic field strength in order to attract the finer particles. At the same time, however, the magnetic rolls also require magnetic field uniformity to avoid undesirable inconsistency across the reprographic image.
Well known materials, such as bonded ferritic magnets, are used in magnetic products, such as the aforementioned magnetic rolls, and have the advantage of high magnetic uniformity, low cost and flexibility. These magnets, however, are limited in magnetic field strength. For example, extruded ferritic magnets are limited to a magnetic field strength of approximately 800 Gauss (G), and consequently are limited in their application.
While other magnetic materials, such as rare earth magnets, may also be used in magnetic products to provide increased magnetic field strength, these suffer from other drawbacks. Although other magnetic materials can exceed the strength of ferrite magnets, (e.g., an approximately 10 mm rare earth, neodymium-iron-boron magnet's magnetic field strength is approximately 1500 G), none approach the strength of rare earth magnets without also suffering from lack of magnetic field uniformity, being costly to produce, and lacking in flexibility.
The aforementioned disadvantages make conventional ferritic and rare earth magnets difficult to use in applications, such as high quality image reproduction, requiring flexible and durable magnets having both high magnetic field strength and high magnetic field uniformity. Hence, an ongoing need exists for flexible and durable magnets and articles having both high magnetic field strength and high magnetic field uniformity at a low cost.